Hello there and thank you for reaching out, I would be curious to see your file if you are able to share it through the "contact us" button, that would be awesome.
Otherwise, the first thing that I would check is if the problem is with flipped faces. Select the object in the scenegraph, and use the double-sided material inside the material setting. If the object appears is because either Datasmith is doing something wrong with flipping faces or the faces were flipped in the original DCC.
Let me know if that helped at all, and please use the contact us so that a support agent can double-check if this is a bug or not.
I'm udating this post since I have the same problem. I had a functional twinmotion linked to my archicad project, and suddenly all the archicad objects stopped appearing.
I didn't find the double-sided material inside the material setting of the scenegraph you mentionned.
I've used twinmotion since released whitout any big issues so I'm confused about this one. I tried to update to the new version of twin, I uninstalled and installed again datasmith. I did evertyhing twice. I tried to change the version of archicad. My project was created on the version 25 and now I migrated on version 26, but it didn't do that the other years so I'm not really sure it's an issue. I will try to share some images below:
When I open the twin file whitout clicking on anything:
Bigger problem: when I try with any other project, old, new, anything, it's doing the same. Nothing. When I click on "zoom on to the object" in the scenegraph, it just zooms on the "xyz with yellow ball on the center" (don't know the name) tool.
Let me know if this issue tells you something and thank you for your help since right now Twin is litteraly not working at all for me...